1. Field of the Invention
This invention relates to an assembling device for a disc cartridge housing a disc such as a magnetic disc or an optical disc used as an information recording medium. More particularly, it relates to an assembling device used for assembling a pair of cartridge halves making up a main cartridge body unit of the disc cartridge.
2. Description of the Related Art
Conventionally, a disc cartridge, housing therein a disc, such as a magnetic disc or an optical disc, used as an information recording medium, is comprised of a main cartridge body unit, obtained on abutting and interconnecting paired upper and lower cartridge halves, formed by injection molding a thermoplastic synthetic resin, and a disc rotationally housed within the main cartridge body unit.
As shown in FIGS. 1(A) to 1(C), on each corner of an inner surface of the upper cartridge half 101 of the main cartridge body unit, housing the disc therein, there is formed a protuberance 103 for coupling the upper cartridge half 101 to a lower cartridge half 102 constituting a main cartridge body unit along with the upper cartridge half 101, as shown in FIGS. 1A to 1C. In each corner of the lower cartridge half 102 is formed a through-hole 104 passed through by the protuberance 103. The upper and lower cartridge halves 101, 102 are interconnected by inserting a disc in the upper cartridge half 101, passing the protuberance 103 through the through-hole 104 to attach the lower cartridge half 102 to the upper cartridge half 101 and thermally caulking a distal end 103a of the protuberance 103 protruded from the through-hole 104.
An assembling device for a disc cartridge, obtained on interconnecting the upper cartridge half 101 and the lower cartridge half 102, includes a thermal caulking head 111 for thermally deforming the protuberance 103, as shown in FIG. 1A. The thermal caulking head 111 has its distal end face recessed substantially hemi-arcuately to form a recess 112, and an abutment 113 for compressing against the lower cartridge half 102 is formed around the recess 112. The thermal caulking head 111 is heated to a temperature which thermally deforms the synthetic resin. With the caulking head 111 in the heated state, the assembling device for a disc cartridge is moved in a direction approaching to the protuberance 103, as shown in FIG. 1B, until the abutment 113 compresses against the outer surface of the lower cartridge half 102. The distal end 103a of the protuberance 103 is thrust by the recess 112, at the same time as it is thermally deformed, so that it is deformed to a semicircular cross-sectional shape after the shape of the recess 112. The deformed distal end 103a becomes larger in diameter than the through-hole 104 to form a retainer 106 which prohibits detachment of the protuberance 103 from the through-hole 104. The caulking head 111 then is moved in a direction away from the lower cartridge half 102, as shown in FIG. 1C, to allow the distal end 103a of the thermally deformed protuberance 103 to be cooled and solidified spontaneously to interconnect the lower cartridge half 102 and the upper cartridge half 103.
Meanwhile, for thermal caulking, the caulking head 111 needs to be heated to a temperature allowing for thermal deformation. In addition, the heated caulking head 111 needs to be cooled to a moderate temperature. Thus, the caulking process is timeconsuming to render it difficult to improve the disc cartridge production efficiency. Should it be attempted to reduce the time needed for caulking, the caulking head 111 cannot be heated sufficiently, with the result that the protuberance 103 formed of the thermoplastic resin cannot be deformed thermally sufficiently. Thus, the distal end 103a of the protuberance 103 cannot be thermally deformed sufficiently, with the result that a sufficient coupling force to interconnect the upper and lower cartridge halves cannot be developed such that the upper and lower cartridge halves 101, 102 tend to be readily detached from each other after assembling.